Flooding and geomorphic impacts in a mountain torrent: Raise Beck, central Lake District, England
Flooding and geomorphic impacts in a mountain torrent: Raise Beck, central Lake District, England
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山洪中的洪水和地貌影响：英格兰中部湖区的 Raise Beck
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
J. Warburton
中科院分区：
文献类型：
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作者：
R. Johnson;J. Warburton
Raise Beck是位于英格兰北部中部湖区丘陵地带（流域面积1.27 km2）的山洪。激流显示了几次大洪水事件的证据，最近的一次是在1995年1月。这一事件导致扇形顶部的主要河道崩裂，使主要洪水流向南方，阻塞了A591主干道，造成了局部洪水。与此事件有关的气象条件是用当地的降雨记录和气候资料描述的。记录显示，洪水发生前24小时的降雨量为164毫米。利用古水文和降雨径流法重建洪峰流量，分别得到27 ~ 74 m3 s−1和4 ~ 6 m3 s−1的流量值。洪水带着高达1400毫米的b轴巨石。这些结果提出了陡峭山区流域洪水估算的一些重要的一般性问题。该事件的地貌影响是通过比较洪水前后的航空照片以及直接的实地观测来评估的。在历史时间尺度上，利用地衣测量法、长期降雨数据和文献记录调查了洪水的影响和发生情况。历史上两次主要的洪水事件发生在19世纪中叶。最近和历史洪水事件的沉积物主导了Raise Beck洪水的沉积学证据，因此该集水区对高震级、低频率的洪水事件敏感。在1995年洪水之后，大部分下游的集水区都采用了裂口堤防，重新建立了向北流向瑟尔米尔的水流。根据对渠道容量的分析，考虑了这一管理策略在控制未来洪水方面可能取得的成功。结论是，渠化方案只是一种短期解决办法，无法控制相当于1995年1月洪水的事件的泄洪。版权所有©2002约翰威利父子有限公司
Raise Beck is a mountain torrent located in the central Lake District fells, northern England (drainage area of 1·27 km2). The torrent shows evidence of several major flood events, the most recent of which was in January 1995. This event caused a major channel avulsion at the fan apex diverting the main flood flow to the south, blocking the A591 trunk road and causing local flooding. The meteorological conditions associated with this event are described using local rainfall records and climatic data. Records show 164 mm of rainfall in the 24 hours preceding the flood. The peak flood discharge is reconstructed using palaeohydrological and rainfall–runoff methods, which provide discharge values of 27–74 m3 s−1, and 4–6 m3 s−1, respectively. The flood transported boulders with b‐axes up to 1400 mm. These results raise some important general questions about flood estimation in steep mountain catchments. The geomorphological impact of the event is evaluated by comparing aerial photographs from before and after the flood, along with direct field observations. Over the historical timescale the impact and occurrence of flooding is investigated using lichenometry, long‐term rainfall data, and documentary records. Two major historical floods events are identified in the middle of the nineteenth century. The deposits of the recent and historical flood events dominate the sedimentological evidence of flooding at Raise Beck, therefore the catchment is sensitive to high magnitude, low frequency events. Following the 1995 flood much of the lower catchment was channelized using rip‐rap bank protection, re‐establishing flow north towards Thirlmere. The likely success of this management strategy in containing future floods is considered, based on an analysis of channel capacities. It is concluded that the channelization scheme is only a short‐term solution, which would fail to contain the discharge of an event equivalent to the January 1995 flood. Copyright © 2002 John Wiley & Sons, Ltd.